1. Field of the Invention
The present invention relates to a superfine copper alloy wire and the manufacturing method therefor, and particularly to a superfine copper alloy wire applied to signal lines for electronic equipment, electric power supply lines and the like.
2. Description of the Related Art
Excellent electric conductivity, strength, flexibility, and wire drawability are required for a superfine copper alloy wire which is wired for inputting/outputting signals to and from a compact electronic equipment or wired for supplying an electric power to such electronic equipment. Heretofore, a Cu—Sn base alloy wire or a Cu—Sn—In base alloy wire being excellent in strength has been employed.
Recently, there is a tendency for thinning a diameter of a conductor in superfine copper alloy wires. To suppress increase in resistance of a conductor accompanied with thinning the conductor, elevation of an electric conductivity in the conductor is desired. In addition, since a wire material becomes also easily broken with a small load, highly strengthening a conductor is required to avoid breaking of the wire material. As a copper alloy wire having a high strength and a high electric conductivity, a Cu—Ag base alloy wire is desired. An example of a method for manufacturing a Cu—Ag alloy wire includes the following methods:
(1) A method for obtaining a copper alloy wire having a high strength and a high electric conductivity wherein a cast rod of a Cu for 2 to 14% by weight Ag alloy is cold-worked and heat-treated. The heat treatment is carried out at a temperature of 400 to 600° C. for one to 100 hours (see Japanese patent application laid-open No. 2000-199042).
(2) A method for obtaining a copper alloy wire having a high strength and a high electric conductivity wherein an ingot of a Cu for 1 to 10% by weight Ag alloy is cold-worked and heat-treated. In this case, the heat treatment is conducted in two steps wherein the first step is conducted at a temperature of 700 to 950° C. for 0.5 to 5 hours, and the second step is conducted at a temperature of 250 to less than 400° C. for 0.5 to 40 hours (see Japanese patent No. 3325641).
(3) A method for obtaining a copper alloy wire having a high strength and a high electric conductivity wherein a copper alloy soft raw material of a Cu for 1.0 to 4.5% by weight Ag alloy is cold-worked and heat-treated. In this case, the heat treatment is conducted at a temperature of 300 to 550° C. for one second to thirty minutes (see Japanese patent application laid-open No. Hei 11-293431).
(4) A method for obtaining a copper alloy wire having a high strength and a high electric conductivity wherein a cast rod of a Cu for 1.0 to 15.0% by weight Ag alloy is cold-worked and heat-treated. In this case, the heat treatment is conducted at a temperature of 400 to 500° C. for 1 to 30 hours (see Japanese patent application laid-open No. 2001-40439).
Incidentally, when a wire diameter of any of the respective copper alloy wires obtained by the methods (1) to (4) mentioned above is made to be 0.008 to 0.05 mm in the form of a superfine wire, it is difficult to achieve both of a high tensile strength of 800 MPa or more and a high electric conductivity of 80% IACS or more.